The present invention relates to a radiographic imaging system and a silver halide photographic light sensitive material, thereby achieving enhanced image quality, and in particular to a noble radiographic imaging system exhibiting high sensitivity and superior image quality, whereby images exhibiting superior sharpness are obtained and which is suitable for magnification mammography.
For diagnosis of breast cancer, specifically diagnosis of breast cancer at the initial stage, for example, is useful a photographic combination for mammographic use which is comprised of a radiographic intensifying screen and a silver halide photographic material (hereinafter, also referred to as a screen film system), whereby micro-calcification having a size of some hundreds micrometers or less can be detected at the initial stage of cancer. Specifically, relatively low speed photographic materials exhibiting superior graininess are employed in the conventional photographic combination for mammographic use. To enhance the detectability thereof, further enhanced sharpness in the screen film system has been desired. For example, a radiographic combination of a silver halide photographic material having a silver halide emulsion layer coated on only one side of a support (a so-called single-sided coated film) and a fluorescent screen (or X-ray intensifying screen) in the back screen arrangement is employed to achieve enhanced sharpness. Further, increasing the contrast of the single-sided coated film or prolonging the developing time in processing is conducted to achieve a contrast-increase in the film.
Although sharpness can be enhanced by a contrast-increase of the film, however, there occurs a self-inconsistency such that the contrast-increase results in deteriorated graininess. For example, not only observation of micro-calcification but also detection of a low contrast image of a tumor having a size of about 1 cm is dispensable in diagnosis of breast cancer. Accordingly, enhancement of sharpness without causing deterioration in graininess is desired in mammography.
Deterioration of graininess caused by a contrast-increase of the film can be improved by increasing the X-ray dose, which must be limited in terms of patient exposure to radiation. Further, an X-ray source of molybdenum is often employed for mammography since the use of an X-ray source giving high exposure to radiation is not suited. Furthermore, there have been made attempts of enhancing graininess of a silver halide photographic material but the size of silver halide grains used in the silver halide photographic material used for mammography is so small that this technique is close to its limitation.
Radiographic film for use in examination of breast cancer comprise a transparent support having a light sensitive emulsion layer only on one side of the support, which contains a relatively large amount of silver halide grains to achieve high contrast and a high density such as 3.5 or more, disadvantageously making rapid access difficult not only in developing but also in fixing, washing and drying.
In radiographic films having light sensitive emulsion layers on both sides of the support, the silver coverage per one side and the content of hydrophilic colloidal material can be easily reduced to provide suitability for rapid access or processing at a relatively low replenishing rate. However, such dual coated films have a concern of a lowering of sharpness, caused by crossover light, as compared to the single-sided coated film. It was found by the inventors of this invention that enhanced sharpness was achieved by the application of the radiography method of thin invention.
Accordingly, it is an object of the present invention to provide an radiographic imaging method by the use of a silver halide photographic material having light sensitive emulsion layers on opposite sides of the support, suitable for magnifying mammography exhibiting enhanced speed and superior sharpness.
The object of the invention can be accomplished by the following constitution:
(1) a radiographic imaging system for making a radiograph by a radiography apparatus using a photographic combination of a silver halide photographic light sensitive material interposed between intensifying screens, the photographic material comprising a support having a light sensitive silver halide emulsion layer on each of both sides of the support, wherein the radiography apparatus conducts making a radiograph under the condition that a distance between the focal point of an X-ray tube and the photographic material is 0.9 to 3.0 m, a distance between the focal point of the X-ray tube and an object is 0.5 to 2.7 m and a distance between the object and the photographic combination is 0.3 to 1.5 m;
(2) a silver halide photographic light sensitive material which is sandwiched between intensifying screens to form a photographic combination for use in a radiographic imaging system for making a radiograph by a radiography apparatus, wherein the radiography apparatus conducts making a radiograph under the condition that a distance between a focal point of an X-ray tube and the photographic material is 0.9 to 3.0 m, a distance between the focal point of the X-ray tube and an object is 0.5 to 2.7 m and a distance between the object and the photographic combination is 0.3 to 1.5 m;
the photographic material comprises a support having a light sensitive silver halide emulsion layer on each of both sides of the support, the photographic material exhibiting a crossover of not more than 15% and an average contrast of not less than 3.4 when the photographic combination is exposed to X-ray and subjected to processing (A), wherein the processing (A) is conducted using a roller transport type automatic processor and the following developer solution (D) and fixed solution (F) at a developing temperature of 35xc2x0 C. for a developing time of 24 to 28 sec. and at a fixing temperature of 33xc2x0 C. for a fixing time of 15 to 25 sec.:
in which water is added to make 1 lit. and the pH is adjusted to 10.25 with an aqueous acetic solution; and
in which water is added to make 1 lit. and the pH is adjusted to 4.55 with an aqueous acetic-acid solution or aqueous sodium hydroxide solution.